Circuit interrupter



un 1944- B. P. BAKER ET AL 2,351,903

CIRCUIT INTERRUPTER Filed A ril 7, 1942 4 Sheets-Sheet l insulation 11 WITNESSES: I PIILgEbIgORS d 4% E erz a/vzzzz a ar an W Herbert J Web :fl/M I 4 BY June 20, 1944. BAKER ET AL5 2,351,903

CIRCUIT INTERRUPTER Filed April 7, 1942 4 Sheets-Sheet 2 WITNESSES:

June 20, 1944. B. P. BAKER ETAL CIRCUIT i'NTERRUPTER Filed April '7, 1942 4 Sheets-Sheet 3 WITNESSES: I INVENTORS Baiy'amz/z PBa/fier and v Herb/3P2 J Web June 20, 1944.

B. P. BAKER ETAL CIRCUIT INTERRUPTER Filed April '7, 1942 4 Sheets-Sheet 4' WITNESSES:

Bari 4 min PBakerand Hegertl 14/652). & IZ/ATTORN Patented June 20, 1944 2,351,903 omcurr m'raanur'rna Benjamin P. Baker, Turtle Creek, and Herbert J.

Webb, Forest Hills, Pa", asslgnors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation otlennsylvanla Application April 7, 1942, Serial No. 437,958

11 Claims. (Cl. 2() 082) The invention relates to electric circuitinterrupters and, more particularly, to circuit inter- .rupters of the fluid pressure operated type.

An object of the invention is the provision of a circuit interrupter with an improved fluid pressure. operating means for controlling the movement of the contact means.

Another object of the invention is the provision of a circuit interrupter with a fluid operating means for effecting high speed operation of the contact means, said operating means embodying an improved fluid shock-absorbing system for smoothly decelerating the end of the stroke.

Another object of the invention is theprovision of a circuit interrupter having a compressed gas operating piston foreffecting'high speed operation of the contact means, and an improved shock-absorbing means comprising anautomatic valve which permits free flow of operating compressed gas into th operating cylinder and which normally throttles the reversely flowing exhaust gas a predetermined amount.

Another object of the invention is the provision of a compressed gas-operated circuit interrupter embodying a shock-absorbing system as described in the preceding paragraph, and whereing the throttle valve throttles the reversely flowing exhaust gas a lesser amount whenever a reverse switching operation occurs within a predetermined short time interval after the valve has been opened by forwardly flowing gas into the cylinder.

Another object of the invention is the provision moving parts at the of a compressed air operated circuit interrupter with an improved air shock-absorbing system comprising an automatic throttle valve which is opened by the forward flow oflcompressed air into the interrupter operating cylinder and closed after a predetermined-short time delay following operation of the breaker, said valve in the closed position acting to partially throttle reversely flowing air exhausted from the cylinder. The novel features that are considered characteristc of the invention are set forth in particular in. the appended claims. The invention itself, however, both as to structure and opera- Fig. 2 is a fragmentary sectional view, on an enlarged scale, showing the contact operating means of the circuit interrupter and the shocktion, together with additional objects and advantages thereof, will be best understood from the following detailed descriptionof apreferred embodment when read in conjunction with the accompanying drawings, in which:

Figure 1 is a side elevational view of a circuit interrupter. embodying the features of the present invention;

absorbing system for the movable disconnect contact member of the interrupter;

Fig. 3- is a detail sectional view on an enlarged scale of one of the automatic throttle valves;

Fig. 4 is a sectional view, on an enlarged scale, of the arcing contact operating means and the dump valves;

Fig. 5 is a fragmentary enlargedview, partly in section, showing the blast valve mechanism; and Fig. 6 is a fragmentary view, partly in'section showing-the opening and closing control valves of the interrupter.

Thefeatures of the present invention are illustrated as applied to a circuit interrupter of the same general construction as fully disclosed in the copending application of L. R. Ludwiget al.,- Serial No. 431,394, filed February 18, 1942, and assigned to the assignee of the present applica-' tion Referring to the drawings, the reference numeral ll indicates a framework which may be formed of structural steel or other suitable material.

l5 and i1, only the first two of which are shown in Fig. i, the latter being shown in Fig. 2. Supported upon the upper endof the insulators l3, l5 and H is a casing IQ for housing the operating means more clearly shown in Fig. 2.. The casing 19 supports a hollow insulator 2| which, in turn, supports a circuit interrupting element 23. A hollow insulator 25 extends upwardly from the element 23 and has a metallic terminal cap 21 secured on its free end. A stationary contact member 29 extends downwardly from the tenminal cap 21 into the circuit interrupting element 23. A movable contact member 3| coacts with the stationary contact member 29 and extends downwardly through the element .23 and through the, hollow insulator 2|. The lower end of the contact member 3| extends into the casing l9 and is connected to a piston of the operating means as shown in Fig. 2, and which willbe more fully described hereinafter.

The contacts 29-3! form arcing contacts of the interrupter and are electrically connected in series with a pair of disconnect contacts which are arranged to be openedafter the arcing contacts open during a circuit opening operation of the circuit interrupter, and closed after the arc- .ing contacts have closed duringa closing opera-' tion of the circuit interrupter. The disconnect Rising from the left-hand side of the framework are a plurality of hollow insulators l3,

contacts comprise a stationary disconnect contact member 83 mounted in a terminal cap I on the upper end oi a hollow insulator 31, and a cooperating movable disconnect contact member I. in the form of a hollow tubular rod which is mounted in bearing means on the casing I! for straight line movement in the direction of its longitudinal axis, the axis of movement the resilient connector contact means II (Fig. 2) slidably engageable by contact member II, and by connector strips 55 and 51 (Fig. 2). The latter conductor strip 51 is electrically connected to a similar connector contact means N (Fig. 2) that is slidably engageable by the movable disconnect contact member 39.

The hollow insulator I! may be supported from the right-hand end of the framework ii, and this insulator serves as a housing for transformers and other suitable instruments necessary for the control of the circuitinterrupteru External circuit connections to the interrupter are made to a terminal 61 carried by the terminal cap 21 and to a terminal Ill on the terminal cap 35. Thus from the foregoing description, it is apparent that when the circuit interrupter is in closed position, current flows through the interrupter from the terminal I, through the terminal cap 21, stationary arcing contact 28, movable arcing contact tl, connector contact means 53, conducting strips 55 and 51, connector contact means 59, movable disconnect contact member 39, stationary disconnect contact member 33 and through a flexible shunt conductor (not shown) to the terminal cap ll and terminal 83. I1 the movable arcing contact 3| is operated to open circuit position while the interrupter is carrying a load, an arc will be drawn by the movable arcing contact member ll. Extinction of arcs drawn by the movable arcing contact member 3i may be accomplished by any suitable arc extinguishing means but preferably by an arc extinguisher or the fluid'blast type which, for

example, may be of the form fully disclosed in the copending application of L. R. Ludwig and B. P. Baker, Serial No. 373,856, filed January9, 1941, and assigned to the assignee of this application. Since the present application is not concerned with the arc extinguishing structure, it is believed that the general designation of the arc extinguishing unit ll will be sufficient for the purpose at hand.

Fluid under pressure, in this instance compressed air, for extinguishing the arc and also for the operating means of the interrupter may be stored in-a tank 81 mounted withinthe framework il. Extending from the left-hand end of the tank 01 is a pipe 89 which has mounted thereon and in communication therewith a blast valve mechanism indicated generally at H. The blast valve mechanism has a housing II (Fig. 5) which communicates through a short section of pipe II with the passage through the interior of the insulator ll. The passage through the insulator II communicates through a pipe 11 and asonooa- II, pipe I1 and tubular insulator It. The blast valve mechanism Ii is of the same construction as that disclosed in the aforementioned copending application of L. R. Ludwiget al., Serial No. 431,394, and consequently only a very brief description thereof will be given since reference to the aforementioned application may be had for details of construction. Briefly, the blast valve mechanism includes a valve 18 in the hous-' member II, and an operating cylinder llil having a double acting piston ill! therein (Fig. 2) connected to the lower end of the movable disconnect contact member The operating cylinder 99 is mounted within the casing 19 and has a lower cylinder head I09 secured thereto by bolts lli'l, the cylinder head being in turn secured to the bottom plate ill of the casing I! by a plurality oi bolts (not shown). Thelower portion oi! the arcing contact rod member Ii slidably extends through the offset portion of the pipe 11 and through an opening provided therefor in the upper head 01 the cylinder ll, the lower end of the contact member being connected to the piston Iiii. Referring to Fig. 4, the cylinder 98 has a projection ll! formed integral therewith adjacent the upper end, and this projection has a passage H5 leading to the upper end of the interior of the cylinder and a port (not shown) in communication with the passage which is connected by a pipe Ill (Fig. 2) to the passage of the hollow insulator ll. This passage of the hollow insulator I1 is, in turn, connected by a pipe ill (Fig. 6) to an opening valve mechanism I63 for controlling the flow of compressed air to effect an opening operation of the circuit interrupter. The lower end of the operating cylinder 89 is also provided with an integral projection l2! (Fig. 4) having a passage I28 therein communicating with the lower end of the cylinder, and also has a port (not shown) in communication with the passage which is connected by a pipe I25 (Fig. 2) to the passage through the hollow insulator II which conducts air for closing the circuit interrupter. The passage of the hollow insulator I8 is, in turn, connected ,by a pipe I21 (Fig. 6) to a closing valve mechanism I" which will be hereinafter described.

The operating cylinder IN is mounted in the casing I! and the upper portion thereof projects outside of the casing it, through an opening provided in an annular casting or supporting member I28 which is secured to the wall of the casing is by a plurality 0! bolts III'. The member I29 serves to support the cylinder IN. The lower end of the operating cylinder I'll fits into a cylinder head ill which is secured on this end of the cylinder by a plurality of elongated bolts I", only one being shown. The bolts I" pass through a flange or the cylinder head I" and thread into the annular supp rt member I". The upper end of the operating cylinder ill iits into a cylinder head III which is secured thereon by a plurality of bolts I, onl one being shown. The bolts I" extend through openings I31. A metallic closure cap provided in a flange oi the cylinder head I31 and a the lower ends of the bolts thread into the angular support member I29, thus securely clamping the cylinder head on the end 01' the cylinder. A metallic cover Ill is mounted at the. upper end of the cylinder head and is secured thereto by a plurality of bolts 3, only one being shown. The bolts Il3 pass through a flange of the cover Ill and through the flange oi the cylinder head 5 is securely clamped over the upper end of the cylinder head I31 by the cover Ill, suitable packing gaskets or other packing material being disposed between the cap Il5and the upper end of the cylinder head I31.

The tubular disconnect contact member 33 extends through bearing openings in the cover I and end cap 5 into the interior of the cylinder I03, and the lower end of this contact rraesmber is connected" to the operating piston I The lower cylinder head I33 oi the operating cylinder I03 is provided with passages H9 and Ill which communicate with the lower end of the interior of the cylinder I03. The compressed air for closing the disconnect contact member is adapted to how through these passages to the underside of the piston I05. The upper cylinder head I31 is also provided with passages I53 and I55 which communicate with the interior of the cylinder head at the upper end of the cylinder I03 for conducting the flow of compressed air to the upper side of the piston I05 to effect opening operation of the disconnect contact member 39.

A sleet hood I51 is provided for protecting the cult interrupter is derived from the air storage tank 01. For this purpose, the pipe 39 is provided with two branch pipes I59 and I5I (Fig;

6). -The pipe I59 leads to the opening valve mechanism generally indicated at I 63, whereas the branch pipe Ill leads to'the closing valve mechanism indicated generally at I35. Gompressed air from the opening valve mechanism I03 is conducted through the pipe Il'9 and passage of the hollow insulator I1 and pipeII1 to the upper end of the operating cylinder 99 above the uppermost position of the operating piston IN. The closing valve mechanism I55 controls the flow of compressed air from the pipe "I, through the pipe I21, passage of the hollow insulator I5 and pipe I to the lower end of the operating cylinder 99 below the lowermost position of the operating piston IOI to effect closing operation of the circuit interrupter.

It is important that the disconnect contact member 39 should be opened only after the arcing contact, member 3| has been moved to full open position during a circuit opening Operation, and it is also desirable that the disconnect contact member 39 should close after the arcing contact member.3l has reached closed position during a closing operation, in order to eliminate the necessity of providing a blast of arc extinguishing fluid for the arcing contact during the closing operation. In order to accomplish this sequence of operation of the contact members 3I and 39, the operating pistons IN and I05 are pneumatically interlocked to insure the desired sequence of operation For this purpose the operating cylinder 99 is provided with a projection I39 (Fig. '4) integral therewithadjacent the u per end, and-this projection has an air passa e I1I formed therein which communicates at one 'end of the operating cylinder I03.

cylinder 99 is so located that it is uncovered by the piston IOI after the piston has moved downwardly a" predetermined distance in an openin direction, so that the operating piston IOI will have overcome static friction and come up to nearly full speed before compressed air is admitted through the pipes I13 and I15 to the upper The construction" is such that movable arcing contact member 3I will have reached full open position before the compressed air applied to the upper side of the operating piston I05 starts to move the disconnect contact member 39 to the. open position.

A similar projection I19 (Fig. 4) is formed integral with the cylinder 99 adjacent the lower end thereof, and this projection has a passage Ill which communicates at one end with the interior oi the cylinder 99 at a point a predetermined distance above the lower end of the cylinder. The other end of the passage I8I communicates with a port (not shown) in the pro- .lection I 19 which is connected by a pipe I83 (Fig. 2) to the passages H9 and I5I of the cylinder head I33, leading to the lower end of the operating cylinder 103. The point of entry of the passage IOI into the cylinder 99 is disposed to be uncovered by the operating piston I'0I after the piston has moved upwardly a predetermined distance in the closing direction, to admit air to the lower end oi. the operating cylinder I03 beneath the piston I05. The location of the passage I3I is such that the arcing contact member will have been moved to the completely closed position before the compressed air acting on the underside of the operating piston I05 moves the interrupter, it is necessary to dump the air in the cylinders ahead of the direction of movement -of the operating pistons to atmosphere so as to prevent air ahead of the pistons from unduly retarding the movement thereof. Two dump valves I31 and I91 (Fig. 4) are provided for this purpose. The dump valve I81 is mounted in the projection I19 at the passage lllthereof. and this valve has a rod I89 connected thereto, the upper end of which .is connected to a piston I9I movable in a cylinder I93 of the projection H3. The dump valve I51 is biased to closed position by a spring 201, and it is adapted to be operated to open position by the piston I9I immediately upon the flow of compressed air to the upper side of the arcing contact operating piston IOI. Opening of the valve I31 opens the lower end of both cylinders 99 and I03 to atmospherethrough an atmosphere exhaust port I95, so that the air below the'twooperating pistons will be at-low pressure and will not unduly retard the openin movement of the two pistons. The other dump valve I91 is mounted inthe projection I09 of the c linder 99 and has a rod I99 connected thereto, the lower end of which is connected to a piston "I mounted in a cylinder 203 of the projection mosphere through an exhaust port 205, thereby causing the air above the operating pistons to be at a low pressure, so that it will not retard the closing movement of the operating pistons.

The opening valve mechanism ill and the closing valvemechanism I" are of the same construction as disclosed in the aforementioned copending application of L. R. Ludwig et al., Serial No. 431,394, and only a brief description thereof will be given in this application, as the details of construction of the valve mechanisms are not necessary to a complete understanding of-the present invention. Referring to Fig. 6, the opening valve mechanism I" has a valve whichis biased closed and which is caused to be opened by air pressure from the pipe illupon energization of a solenoid 2. Similarly, the closing valve mechanism I has a valve 2i! which is biased closed and which is caused to be opened by compressed air from the pipe ll l upon energization of a solenoid 2". The valvemechanisms I" and ill are pneumatically interlocked by means of a piston (not shown) in the valve mechanism I" and by a pipe 2" connecting the housings of the valve mechanisms it! and ill as disclosed in the aforementioned copending application of L. R. Ludwig et al., Serial No. 431,- v

394, so that an opening impulse will always 'take precedence over a closing impulse.

The control circuits for controlling the solenoid V ll of the blast valve mechanism II and the solenoids 2H and 2" of the opening and closing valve mechanisms are the same as disclosed in the aforementioned copending application of L.

H. Ludwig et al., Serial No. 431,394, and are not shown in this application as the details thereof are not necessary to a complete understanding of the present invention. It is suflicient to state that the solenoid 32 of the blast valve mechanism and the solenoid 2H of theopening valve mechsnism are adapted to be simultaneously energized to eflect opening of their respective valves in response to the operation of an opening relay. The

opening relay is caused to be energized in response to the operation of an overload current responsive protective relay or by the closing of a manual opening control switch. The solenoid I! of the blast valve II is caused to be deenergized by auxiliary contacts of an auxiliary switch means 22! (Fig. l) as soon as the disconnect contact member it starts its opening movement; consequently, the blast valve H is returned to its closedposition. As soon as the opening operation of the circuit interrupter is completed and the disconnect contact member 88 reaches full open position, the opening relay is deenergized by the opening of another pair of auxiliary contacts of the auxiliary switch means 22i, so that the opening valve returns to closed position. The solenoid III or the closing valve means is caused to be energized by the operation of a closing relay. The closing relay is, in turn, caused to be operated by either a reclosing relay or by a manual closing control switch. As soon as the closing operation of the circuit interrupter has been completed and the disconnect contact member II has reached the fully closed position, the closing relay is deenergized by the opening of a pair of auxiliary contacts of the auxiliary switch means 22i.

The auxiliary switch 22i (Fig. 1) may be of any conventional multipole construction and is adapted to be operated in accordance with the position of the movable disconnect member It. by means of a rotatable twisted square rod 222 rotatablymounted in the lower head ill and extending into the cylinder ill for substantially the entire length of the cylinder. The contact member 33 is of tubular construction, and the operating piston I" has a square opening (not shown) in alignment with the tubular contact member for slidably engaging the twisted square rod 222. The operating piston IOI and tubular contact member I! slide telescopically on the twisted square rod 222 and rotate the rod in one direction or the other depending upon the direction ofv movement of the operating piston. A crank 22! (Fig. 2) secured to the lower end of the twisted square rod is connected by a linkage rial No. 431,394.

cylinder I03.

The piston IM which drives the arcing contact member II has a relatively short stroke and as a resultcan be safely decelerated by a mechanical bumper means. The contact member 3!, however, is driven by the operating piston ill which has a long stroke, and because of this and the high speeds attained during its travel, it must be decelerated considerably before the end of its stroke in order to prevent damage to the apparatus from shock and impact at the end of the stroke. In accordance with the present invention, the operating means for the movable contact member 33 is provided with an improved air shock-absorbing means for decelerating the contact member I! and its operating piston iii! as these elements approach the end of the operating stroke, and to bring these moving elements to rest at the extreme end of the stroke without shock, stalling or rebound. The shock-absorbing means comprises an automatic throttle valve associated 'with each end of the contact operating Each valve permits free flow of compressed operating air in a forward direction into the corresponding end of the cylinder and is operative to partially throttle the reversely flowing air being exhausted from the corresponding end of the cylinder to thereby decelerate the moving piston by the dashpot action of the air being compressed by the moving piston. Each automatic valve is also operative to remain in open position after it is opened by forwardly flowing air for a predetermined short time inten-val after the forwardly flowing operating air is shut off so that the valve element will thereby exert either no throttling effect or a lesser throttling eflect if a reverse switching operation occurs within a predetermined time interval after the initiation of the preceding switching opera- OIL- Referring to Figs. 2 and 3, each of the automatic valve devices comprises a piston-type cupshaped valve element 22! associated with the air passage leading to the corresponding end of the contact operating cylinder IN.- The valve element 225 is slidably mounted in a valve cylinder 231 which is threaded into an opening provided therefor in the corresponding head of the passage leading to the end of the cylinder.

sage I43.

contact operating cylinder I03 adjacent the air valve element 235 is biased to closed position against its valve seat in the air passage by means of a helical compression spring 233 which is disposed between the automatic valve element 235 and the closedend of the valve cylinder 231. A small bleeder passage 240 is provided in the valve cylinder 231 adjacent the closed end thereof for a purpose which will be hereinafter described.

One of the automatic valve devices is mounted in the cylinder head I31 for the upper end of the contact operating cylinder I03 and the piston type valve element 235 of this valve device is associated with the air passage I53 which communicates with the upper end of the operating cylinder I03. The valve element 235 is biased to closed position against a valve seat 2|I pro-- vided in the passage I53, and the valve seat is provided with one or more leak holes 243 connecting the passages I53 and I55 for the purpose of providing a predetermined degree of throttling of the air being exhausted through the passage stalling or rebound and without developing high impact forces.

The other automatic valve device is of the same construction and is mounted in the lower cylinder head I33 of the contact operating piston. The automatic valve 'element 235 for this end of the contact operating cylinder is associated with the passage I43 leading to the lower end of the contact operating cylinder I03, and the valve spring 233 biases this valve element to closed position against'aseat 2 provided in the pas- The valve seat 2 is provided with one or more leak holes 233, the same as described in connection with the valve device for the upper end of the contact operating cylinder.

When compressed air is caused to flow through the pipe Ito effect movement of the disconnecting contact member 33 to open position, the

air impinges against the automatic valve piston 235, causing it to recede into the valve cylinder 231 against the restraining force of the spring contact operating cylinder I03,to move the operating piston I05 and disconnect contact mem ber 33 downwardly to open position. If no furtheroperation takes place within a predetermined short time interval, the piston valve 235 is returned to closed position by the biasing Thedeceleration would be many times higher than on a normal closing operation, if thevalve element 235 returned immediately to closed position. Since the valve element 235 requires a predetermined time interval to return to closed position, it will. exert a. lesser degree of throttling effect on the air being exhausted through the passage I53 if a reclosing operation occurs within the predetermined time interval after an open..

ing operation. Thus, the degree of shock ab-' sorption may be substantially the same on quick reclosing operations as in the case of normal closing operations.

During the movement of the contact operating piston I05 to open position, the throttle valve 235 associated with the lower end of the contact operating cylinder I03 serves to partially throttle the air being exhausted from the lower end of the contact operating cylinder below-the operating piston I05. The opening movement 01' the contact operating piston is thus decelerated as the piston approaches open position, that is to say, its-lower end position.

' When compressed air is caused, to flow through the pipe I83 to operate the contact member 33 to closed position, the operating air impinges against the piston valve 235 associated with the lower end of the operating cylinder'causing the valve element to recede into the valve cylinder against the force of the spring 233. Thus, this valve element is moved to open position and lets the driving air flow freely throughthe passages I 33 and I5I into the lower end of the contact operating cylinder to move the operating piston I05 to the upper end of the operating cylinder and close the switch. The upper valve 235 for the upper end of the cylinder throttles the air exhausted from the upper end of the cylinder to decelerate the movement of the piston as it approaches its upper end position. If no further operation takes place within a predetermined short time interval, the valv element 235 is returned to closed position after the flow of operating air is shut off by the closing valve mechanism I55. However, if a switch opening operation occurs. immediately after, or within a-short predetermined time interval after, the switch closing operation,- the piston valve 235 is still in spring 233 after the opening airv is shut off by the closing 03 the opening valve mechanism I53.

. This opening valve mechanism I53 has a leak hole (not shown) which allows the air in the pipes I15 and H1 to leak. out to atmosphere after closing oi the opening valve mechanism. The

' short predetermined time interval required for the valve element 235 to return to closed position is determined, however, by the size or bleeder passage 230. This time delay is very important it the switch is to be closed immediately after the opening operation. In this case, there will still be high pressure air in the portion 01 the.

operating cylinder I33 above the operating pisopen position and, consequently, exerts a lesser degree of throttling on the air being exhausted from below the contact operating piston I05 than in the case of a normal opening operation, when the valve is in its closed position.

It is believed that the details of operation of the circuit interrupter will be clearly understood from the foregoing description. Briefly the operation of the circuitinterrupter is as follows: Assuming the circuit breaker to be in open positiori as shown, a closing operation of the circult breaker is caused to take place upon energization of the solenoid 2I5 of the closing valve mechanism I55. Opening of the valve I55 causm compressed air to flow from the tank into the lower endot the arcing contact operating cylating cylinder 33 immediately causes opening of the dump valve I31, thereby establishing an exhaust connection to atmosphere for the upper ends of each of the cylinders 33 and I03. After the arcing contact operating piston ,IOI is moved upwardly a predetermined distance, it uncovers the passage I8I so that compressed air then flows ton I35 and the degree of shock absorption or through the pipe I33 to the lower end of the assmos a throttle valve associated with said passage having a closed position in which it partially throttles the flow oi fluid out or said'cylinder through said passage; said valve being biased to closed positionand operated to open position by the forward flow of fluid into said cylinder through said passage to permit free forward flow per end of the operating cylinder I is in closed of the valve Ill causes compressed air to flow from the tank -61 into the upper end of the arcing contact operating cylinder 89 to move the arcing contact member 8| to open position. The flow of compressed air to the upper end oi the operating cylinder II immediately causes opening of the dump valve Ill, thereby opening the lower ends of both cylinders 88 and 103 to atmosphere through the exhaust port I95. After the operating piston llll is moved downwardly apredetermined distance, it uncovers the passage I'll so that compressed air then flows through the pipe I15 to the upper end of the disconnect W contact operating cylinder I". This flow of compressed air efl'ects opening operation of the disconnect contact member 3!, driving the piston I" downwardly to the lower end of the cylinder. The automatic throttle valve 235- ior the lower end of the operating cylinder III! is in closed position, and in this position acts to partially throttle the air being exhausted from the lower end of the disconnect contact operating cylinder IIII, thereby decelerating the movement or the piston I05 as it approaches its lower end position.

As previously pointed out, each 01 the automatic valves 23! is opened by the forwardly flowing operating air and remains open-for a predetermined short interval or time after the forwardly flowing operating air is shut off. By reason oi this time delay action in the return of the valve members 235 to closed position, these valves will exert a lesser amount of throttling eiiect whenever a reverse switching operation occurs immediately, that is within a predetermined short time interval after the preceding operation.

Thus, the degree oi shock absorption will be subr stantially the same for quick reverse switching operations as for normal operations.

While the invention has been disclosed in accordance with the provisions oi the patent statutes, it is to be understood that various changes in the structural details thereof may be made without departing from some oi the essential features thereof. It is desired, therefore, that the language oi the appended claims be given the broadest reasonable interpretation permissible in the light of the'prior art.

We claim as our invention:

1. A circuit interrupter having a movable contact member, operating means comprising an operating cylinder and a piston in said cylinder for actuating said contact member, means forming a fluid passage communicating with one end of said cylinder for the flow oi fluid into and out of said cylinder, means for supplying fluid under pressure to said cylinder through said passage,

of fluid, and means for delaying the return of said throttle valve to closed position for apredetermined time interval after each opening thereof.

2. A circuit interrupter having a movable contact member, operating means for actuating said contact member comprising an operating cylinder, a fluid pressure operated piston in said cylinder connected .to said contact member,

means for supplying fluid under pressure to said cylinder to actuate said contact member, means for automaticallyexhausting fluid ahead of the moving piston and a valve device for normally throttling the exhaust oi fluid from said cylinder a predetermined amount and ior'throttling the exhaust or fluid a'lesser amount when a reverse operation oi the contact member occurs within a predetermined time interval after initiation oi the preceding operation of the contact member.

3. A circuit interrupter having a movable contact member, operating means for moving said contact member to open and to closed position comprising an operating cylinder, a piston in said cylinder connected to said contact member, means for supplying fluid under pressure to one end of said cylinder to eflect closing operation of the contact member, said operating means including means for automatically exhausting fluid from said one end of the cylinder during opening operation of the contact member, and

a valve device normally operative to throttle the;

comprising an operating cylinder, a piston in said cylinderconnected to said contact member, means for supplying fluid under pressure to said cylinder to efl'ect opening operation of said contact member, means for automatically exhausting fluid from said cylinder ahead 01' the moving piston, and a valve device normally operative to throttle the exhaust of fluid from said cylinder a predetermined amount and operative to throttle the exhaust of fluid a lesser amount 11 a closing operation is initiated within a predetermined time interval after the initiation of an opening operation.

5. A circuit interrupter having a movable contact member, operating means comprising an operating cylinder, a piston in said cylinder for actuating said contact member, means for supplying fluid under pressure to one end of said cylinder to operate said piston, means for automatically exhausting fluid from said end 0! the cylinder upon reverse movement oi. said piston, said last mentioned means including an automatic throttle "alve biased to a closed position in which it throttles the exhaust oi fluid from said cylinder a predetermined amount, said valve being moved to an open position when fluid un der pressure is supplied to said one end oi the 

